1. Field of the Invention
The present invention relates to a light emitting device such as a vertical resonance type planar light emitting laser to be used in an optical integrated circuit or a display, and a method for manufacturing the same.
2. Related Background Art
Several methods have been used to manufacture a substrate reflection mirror of a vertical resonance type planar light emitting laser which has been used as a light emitting device. For example, as shown in FIG. 1, a double hetero-structure 1 is epitaxially grown on a single crystal substrate 2, and a portion of the single crystal substrate is removed to reach a resonator area, from the opposite side to the grown surface. A multi-layer film 3 comprising alternate laminations of two dielectric materials having a large difference in refractive indices is formed in the removed area, and it is used as a substrate reflection mirror. This method has been proposed by IGA et al in the pre-papers of 1988 Spring Technical Conference of the Institute of Applied Physics of Japan, 30a-Zp-4. Further, as shown in FIG. 2, a method of forming a reflection mirror 4 on a substrate 2 by laminating single crystal semiconductors having different refractive indices has also been proposed by IGA et al in the pre-papers of 1988 Spring Technical Conference of the Institute of Applied Physics of Japan, 30a-Zp-5. In this method, the double hetero-structure 1 is formed on the reflection mirror 4.
However, in the former method, a process to etch the substrate is necessary, and as a result of which the strength-is-lowered. In the latter method, the semi-conductor multi-layer film which forms a reflection mirror must be grown by the single crystal. As a result, the material to be used is restricted and it is not possible to make the difference of refractive indices of the layers large. In the multi-layer film having a small difference in the refractive indices, it is necessary to laminate several tens of pairs of semiconductor layers in order to attain a high reflection coefficient, and the film thickness must be strictly controlled. Further, because the number of layers laminated is large, electrical or optical absorption increases.
On the other hand, a method of growing a single crystal on an amorphous or polycrystalline substrate by forming planes having different nucleus formation densities on a substrate surface has been proposed in EC Laid-Open Patent Application No. 244,081. A technique to manufacture a liquid emitting diode (LED) by the use of the above method is disclosed in EC Laid-Open Patent Application No. 285,358. Such methods are hereinafter referred to an selected nucleus formation method.